Study on the Thermal Degradation Mechanism Model of Polystyrene Insulation Materials Under Ultraviolet Aging

ABSTRACT

Expanded polystyrene (EPS) and extruded polystyrene (XPS) are extensively employed as thermal insulation materials in buildings. However, facade spalling exposes these materials to ultraviolet radiation, triggering progressive aging that compromises their thermal stability. Therefore, thermogravimetric analysis was performed to evaluate ultraviolet aging effects on the thermal degradation behavior of EPS and XPS, and further reconstruct their kinetic mechanism models. The results showed that EPS changed from white to yellow, while XPS turned from blue to dark. EPS exhibited extensive fragmentation at 135 days of aging, whereas XPS showed such fragmentation as early as 90 days. The activation energy of EPS increased from 175.32 to 214.90–260.07 kJ/mol and then decreased to 45.58–115.03 kJ/mol, whereas that of XPS continuously decreased from 129.05 to 48.51–89.46 kJ/mol. Furthermore, the kinetic compensation effect, reflected by a significant linear relationship between the pre‐exponential factor and activation energy, was confirmed with R ² values as high as 0.9996 and 0.9999, respectively, thereby validating the reliability of the calculated kinetic parameters. Finally, the thermal degradation mechanism models of the two materials were reconstructed as f ( α ) =  a·α ^m · (1‐ α ) ⁿ . This study provides a theoretical foundation for aging analysis of insulation materials and parametric support for fire prevention.